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< prev - next > Energy Hydro power KnO 100023_River Turbines (Printable PDF)
The hydro-kinetic turbines are
designed to generate electricity
solely from the kinetic energy of
running water in a river or from
tidal currents when used in marine
settings. The conventional
technique of generating electricity
from hydrological energy is done
using water from a high position
that falls through a head onto a
turbine, where water is channelled
along canals and pipes in order to
make use of its potential energy.
This approach is covered in the
Practical Action technical brief on
micro hydro.
The use of kinetic energy from
river currents energy is a less
Figure 1: A river current turbine in Peru. Photo: Soluciones
common, alternative approach to
hydro power where there is zero
head. The energy is converted into
electricity or used directly to power a mechanical water pump for irrigation.
Making use of kinetic energy of river currents was a traditional way to mill flour along with
wind power but was gradually replaced by fossil fuel systems. There is now renewed interest in
river current turbines in a wide range of countries for electricity generation. Practical Action
has been involved in promoting small-scale turbines to provide electricity to remote villages in
the Amazon and to supply water for irrigation in Sudan.
The power available from the river
Most of the principals of this type of turbine are based upon wind turbines, as they work in a
similar way. The power available (Pa ) in watts can be worked out using the following formula.
Pa = ½ x Cp x ρ x A x v3
A = area in metres squared (m2)
ρ = density of water (1000 kg/m3)
V = velocity of water (m/s)
Cp = the power coefficient = 16/27 = 0.592 (theoretical maximum power available)
The theoretical maximum power available from the river is expressed by the equation above
using a power coefficient of 0.592 or 59% efficiency. But a small-scale river turbine has its
own losses which will reduce the power coefficient to around 0.25.
The significant aspect to the equation is that the power increases in a cubed relationship to
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